We describe a laboratory plasma experiment and initial
experimental results which give insight into the
magnetohydrodynamics (MHD) of accretion disks and jet
formation. We utilize a magnetized plasma gun with
concentric electrodes to simulate the topology of a
star-disk system. The inner electrode, which respresents the
star, is a 20.3~cm disk. The outer electrode, which
represents the accreting disk, is an annulus with outer
diameter of 50.8~cm. Our plasmas satisfy the MHD criteria
(S \gg 1, \rho\rm i \ll L, and V\rm A \ll c,
where S is the Lundquist number, \rho\rm i the ion
gyro-radius, L the plasma size, and V\rm A the
Alfvén speed) and are allowed to evolve and expand
freely with minimal interaction with the vacuum chamber
walls which are far away. Using a high-speed multiple-frame
CCD camera, we have obtained high quality images of the
formation and evolution of three distinct plasma regimes,
each corresponding to a possible accretion disk/jet
phenomenon. The regimes depend on \alpha\rm gun=\mu0
I\rm gun/\psi\rm gun (where I\rm gun is the gun
current and \psi\rm gun is the poloidal magnetic flux
linking the gun electrodes). For low \alpha\rm gun, a
plasma column forms along the geometric axis of the gun and
persists for many Alfvén times (\tau\rm A ~
1~\mus), as required for a stable astrophysical jet. For
intermediate \alpha\rm gun, the column develops a
coherent helical perturbation when \alpha\rm gun L
\gtrsim 4 \pi, where L is the column length. This
condition is equivalent to the Kruskal-Shafranov limit,
indicating that the observed instability is an ideal
current-driven instability which strongly affects global
column structure. For high \alpha\rm gun, the plasma
detaches from the plasma gun and propagates along the
geometric axis at a significant fraction of the estimated
Alfvén speed (V\rm A ~50~km/s). The detachment
process may be related to disk winds and flares and other
quasi-periodic behavior associated with accretion disks. The
experimental results support a unified picture of accretion
disk and jet MHD based on magnetic helicity injection and
plasma relaxation. The processes are remarkably similar to
the dynamics of spheromak formation in magnetic fusion
research.